feat(series): add title search to the series page

[magrhino]

Summary

When a library has many series, finding a particular one on the Series page requires scrolling or using the browser's Ctrl+F. Add an in-page title search matching the Authors and Books search fields so users can narrow the series list as they type.

• Reuse the existing case- and accent-insensitive matching helper without additional API requests.
• Show a no-match message and restore all series when the search is cleared, while preserving empty-library guidance.
• Add focused coverage, update the README and Series wiki, and include one changelog fragment.

Existing issues were searched in the fork and upstream; no directly matching issue was found.

Checklist

• Commits signed off with git commit -s
• Tests added or updated
• docs/DEPLOYMENT.md updated if env vars, config, or upgrade path changed — N/A: no deployment changes
• Added a changelog fragment under changelog.d/; CHANGELOG.md untouched
• Wiki pages updated for user-facing behavior (docs/Hardcover-Series-Wiki.md)

Test plan

• make check — not run; validation scoped to the frontend-only change
• cd web && npm test -- SeriesPage.test.tsx — 24 tests passed
• cd web && npm test — 943 tests across 82 files passed
• cd web && npm run lint — passed with 9 existing warnings
• cd web && npm run typecheck
• cd web && npm run build — passed with the existing bundle-size warning
• git diff --check
• make changelog — fragment previewed
• Desktop and mobile browser checks with mocked series data, including accent-insensitive filtering

Local PRScan review found no actionable findings. No backend, container, or release checks were run because those paths are unchanged.